The proposed research is designed to assess the role of gonadal hormones in the induction and display of intraspecific aggressive behavior in the infraprimate mammal. This will be accomplished, in part, by determining the effect upon later aggression of prenatal exposure to androgen. The mechanism through which such early androgen exposure influences fighting will be explored by administering the hormone alone and in combination with an anti-estrogenic or anti-aromatizing agent. If androgen yields its effects via conversion to estrogen, the latter two substances should block the effect of androgen.